A preformed coil of the generic type is known from EP 1 780 871 B1. Here, the individual coils are first spirally wound flatly around an axis running radially inside the finished preformed coil and only then deformed by bending into the finished shape. In order to primarily prevent damage due to mechanical overload, like overstretching of the wire, in areas in which the respective radial offset must be formed, there is the provision according to that document that each coil exhibits additional wire material as a feed line, for example in the form of hair-pin shaped fillets, to facilitate the offset, since additional wire material is required during the production of the offset by a subsequent bending deformation of the completely wound and, as a rule, thermally cemented, preformed coil, in order to prevent an overstretching of the wire in this area. Damage due to deformations of the finished preformed coil can, however, occur; since the wire material can be mechanically overloaded, disadvantageous wire cross-sectional changes as well as damage to the thermosetting varnish coating by tearing or even chipping can occur especially in the area in which the force required for the bending deformation must be applied. Furthermore, the so-called feed line must be very exactly fitted to the required offset; if the feed line is too short or too long, the respective offset cannot be optimally formed without mechanical overload.
DE 101 14 129 A1 likewise describes a tubular, in particular hollow cylindrical, ironless, self-supporting winding of an electric motor, wherein the overlapping preformed coils are formed without radial offset sections with only one radius of curvature. On assembly of the preformed coils to form an entire winding, subsequent deformations and consequent mechanical stress occur, especially in the axially opposite areas in which, because of the overlapping preformed coils, a transition between an inner cylindrical area and an outer cylindrical area, on which the preformed coils rest, must occur.
The underlying object of the present invention is to improve a preformed coil of the type named at the outset, such that damage to the wire material and to its wire cross-section as well as to the area of the offset sections and on the insulation layer of the wire material are prevented during its formation, and that the course of the wire element in the areas of the offset sections is optimized. In addition, an improved, simple and economically feasible manufacturing process should be specified, and a constructively simple and efficient manufacturing device should be made available.